The present invention relates to the manufacture of fuel rails for retaining and supplying fuel to fuel injectors on internal combustion engines; more particularly, to devices useful in quality assurance testing of manufactured fuel rails prior to insertion of fuel injectors therein; and most particularly, to a testing apparatus for determining the acceptability of an injector-receptive gland on a fuel rail.
The use of fuel injectors to meter fuel to the individual cylinders of a multi-cylinder internal combustion engine is well known. Typically in a modern engine, each fuel injector is mounted in an individual socket or gland of a xe2x80x9cfuel railxe2x80x9d which is essentially a manifold formed of tubing in such a configuration that, when the fuel rail is attached to its appropriate engine, each injector is positioned at precisely the correct location for service to its own cylinder. The fuel rail thus supports and positions each injector and also is a reservoir for supplying fuel to each injector upon demand therefrom.
Plated fuel rails and the processes associated with inserting fuel injectors into fuel rail sockets are also well known in the art. A typical fuel injector is an elongate, generally cylindrical device including an elastomeric O-ring disposed in an annular circumferential groove for sealing against the inner wall of a fuel rail seal gland to prevent leakage of fuel past the injector when the fuel rail is full and pressurized. During assembly of the finished fuel rail, the injector insertion process employs sufficient force to compress the O-ring by overcoming the frictional forces that occur between the O-ring and plating on the inner wall of the gland. It is well known in the art that excessive thickness of the plating, caused by normal variation in the plating process, can result in frictional forces that exceed the capability of the insertion tooling. In such events, major disruptions can be created in the sequence of manufacture, which are costly in downtime and materials. Even when insertion is effected, excessive insertion force can result in unacceptable, and sometimes unsuspected, damage to the fuel rail gland, the fuel injector, the O-ring, or combinations thereof.
Several analytical control methods are known in the art which have been employed with varying degrees of success to control and predict the acceptability of plated fuel rail glands. Such methods include static force analysis, surface finish analysis, microscopic visual analysis, and visual transform analysis. All such methods have disadvantages. All except visual transform analysis require very expensive and delicate instrumentation which is easily compromised in a plating environment. Static force analysis can be an inadequate predictor of injector insertion, which is a dynamic process.
What is needed is a simple, repeatable, dynamic test apparatus and method that accurately simulates, and therefore correlates well with, the actual insertion of a fuel injector into a fuel rail gland.
It is a principal object of the present invention to provide a simple, inexpensive, and reliable method and apparatus for acceptance testing of a fuel rail seal gland.
It is a further object of the invention to provide a method and apparatus for acceptance testing of a fuel rail gland that is readily usable in a plating environment.
It is a still further object of the invention to provide such a testing method and apparatus which provides an unambiguous xe2x80x9cpass/failxe2x80x9d result.
Briefly described, an acceptance tester for a fuel rail seal gland drops a weight of predetermined mass under gravity to drive a simulated fuel injector dynamically at the opening of a gland to be tested, simulating accurately the mechanics of insertion of an actual injector into the gland on a production line. The force of insertion may be varied by varying the weight to be dropped, the height from which the weight is dropped, or both. A xe2x80x9cpassxe2x80x9d is indicated when the simulated injector and O-ring are successfully inserted into the gland without damage to the gland or O-ring. Conversely, a xe2x80x9cfailxe2x80x9d is indicated when the simulated injector and O-ring fail to be inserted into the gland, are damaged by insertion, or damage the gland during insertion.
A maximum acceptance force for a given combination of gland and fuel injector can easily be determined empirically. A continuous process for plating fuel rails having glands already attached then may be readily controlled by testing plated glands at statistically significant intervals. This permits operators to accurately monitor plating thickness inferentially.